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Where is the Sun Now?
Sun is closest in early January
- 3.4% more incident energy than average
Sun is farthest away in early July
- 3.4% less incident solar energy than average
Nearly 7% total solar variability over a year
- Corresponds to a 4˚C difference in temperature
Peak aphelion/perihelion differences are > 20%
Notes:
There's a lot more variability in the incident solar energy than many think. This is partially because most of the published solar irradiation data is normalized to 1 AU. Many have used normalized data in an attempt to show that solar variability is unimportant. The 7% difference that currently exists results in more than a 4˚C difference in hemispheric seasonal surface temperature, before
even considering any symmetry differences.
When the Earth's orbit is the most elliptical, the peak differences can reach 23%. Without considering any other factors, this corresponds to about a 15˚C difference in the average temperature of the hemispheres.
When all factors are considered, and aligned in the same direction, the difference can increase to more than 30˚C.